Timing mechanism



s. J. SMITH ET AL 1111 116 MECHANISM Sept. 8, 1953 3 Sheets-Sheet 1 Filed Oct. 24, 1951 INVENITORS. J 5m fly. -u, HTTORMZ-F Sept. 8, 1953 s. J. SMITH ETAL 2,651,361

TIMING MECHANISM Filed Oct. 24, 1951 3 Sheets-Sheet 2 INVENTORS. Stanley J 52224271 7 Jack jTs'rccli JYTTORNEYS'.

linearly moving control member forming part of the operating unit which is adapted to control the operation of one or the other of alternative functions to be performed. The timing mechanism operates under control of master switches which are actuated to cause cyclic operation of the one of said functions in a time preselected therefor, the switches when inactive, being arranged to leave the mechanism in condition to control the other of said functions; whereby occasional operation of said one function can be had by means of said switches, said other function being normally maintained with the mechanism in condition to accept and perform said one function when called upon to do so by actuation of said switches.

In a preferred form, the timing mechanism comprises a motor drive unit which includes a motor having a rotor and stator, the rotor thereof having limited angular movement, of 90 for example, in one direction only, with spring return in the reverse direction. A brake time-delay unit is coupled with the rotor so that the time of completing the limited angular movement is delayed, the delaying mechanism being preferably adjustable to give a range of time cycles for the angular movement of the rotor. The delayed output from the motor controls an electric switching circuit which places a control unit, such as a three-way hydraulic valve, in one position where,

for example, the pressure port of the hydraulic valve is in communication with the control port for actuation of a control mechanism and in an alternative position where the control function is dormant, such as with the pressure port of the I hydraulic valve being in communication with the return port.

Upon actuation of switching means, the dormant condition is electrically energized to give the control condition for the time determined by the motor and brake delay units, whereafter the dormant condition is again automatically set up.

In case of power failure of the electric supply to the circuit, the apparatus is automatically placed in control condition, in the preferred embodiment of the invention.

One specific application of the timing mechanism of the present invention, which exemplifies its utility and advantages, is in connection with the landing gear of aircraft in order to remove the hydraulic pressure from the actual operating means for swinging the landing gear into and out of landing position during the long periods of non-use, namely, the dormant periods between the occasional periods of operation of the landing gear. By ganging the switching means of the electric time-delay control circuit according to the present invention, with the switching means directly causing the movements of the landing gear, hydraulic power can be supplied to the landing gear controls only when called for and when needed for operation thereof.

Referring now specifically to the drawings, Figs. 1-5, the timing mechanism is housed in a casing in, preferably of aluminum or other lightweight metal and comprises a timer unit H and a valve assembly [2. Thetimer unit consists of three cooperating elements which together serve to give the timedelay control as hereinafter brought forth. are: a motor drive unit l3; a M; and an operating unit IS.

The motor drive unit l3 comprises a rotor 15 having coil windings 18 to move same. Shaft These elements brake-delay unit [8 is mounted for antiof the valve unit,

I1 and mounted upon ashaft frictional rotation in ball bearings [9 which are fixedly supported in the casing 10 by brackets 20a and 20b attached to the casing in conventional manner. The stator of the motor comprises a pair of opposed pole pieces 22 and 23 each mounted on the casing H) by means of ribs 24 and 25 suitably attached to the casing and carrying the pole pieces in fixed position by means of screws 26 which are threaded into bores in the pole pieces. One of said screws comprises a head screw 21 which is adapted to cause association of delay unit H and valve assembly i2 by having the head of screw 2! slidable within a groove 28 in the casing of the valve assembly i2 (see Fig. 1). Stator windings 29 are associated with pole pieces 24 and 25 to provide the excitation necessary to cause rotation of the rotor 16.

It is one of the important features of the present invention to provide unidirectional limited angular movement of rotor 16 in an amount which is preselected for the desired conditions of operation of the timing mechanism. To this end, as shown in Figs. 4 and 5, pole pieces 22 and 23 are formed with their exposed faces of limited area and so shaped as to be eccentric to the rotor shaft [8, whereby in one direction of rotary movement of the rotor 15, the air gap between the pole pieces and rotor will diminish its size from a maximum at the starting point to a minimum at the finishing point. The pole pieces 22 and 23 are specifically shown as segments whereby the rotation of the rotor will be only through 90, to give the limited angular movement desired. Obviously, other angular limits can be given by having eccentric pole pieces 22 and 23 formed as greater or lesser angular segments.

When the motor windings are excited, rotation of rotor i6 through the 90 angular distance will take place, due to tendency of the flux to seek the shortest path across the air gap, and this movement will be unidirectional. Upon disconnection of the exciting current, rotor 16 is returned to starting position by a torsion spring 30 mounted on shaft 18 at one end and fixed to bracket 20a by a stud 3! at the other end, the spring being wound up by angular movement of rotor IS with sufiicient torsion to rotate the rotor back to zero or starting position when the electric current is disconnected. This type of motor avoids the use of commutators and consequent radio interference therefrom.

Normally the lapse of time between start an finish of rotation of rotor 16 will be determined by the characteristics of rotor, stator and operating parts and will be substantially a fixed period of time.

It is another important feature of the present invention to provide a time-delay means in which the time cycle can be varied over a wide range, to suit varying conditions of operation. To this end, brake-delay unit i4 is provided, comprising a gear box 32 which is a step-up transmission device to obtain a number of revolutions at its output for the 90 or A revolution of rotor l6, as an input, the input shaft 33 of gear box 32 being coupled to shaft i8 by a spring clutch 34. Clutch 34 is unidirectional and comprises a helical spring 36 fixed on shaft (8 by clamp 35 to move therewith, spring 36 being twisted in one direction of rotation into gripping contact with shaft 33 which is surrounded by part of the spring, to cause it to follow turning movements of shaft [8. In the reverse direction spring 36 will slip upon shaft 33 and have no driving effect thereon. Thus, the input shaft 33 will follow movements of 'roton lfi and the outp t shaft 31 ot 'gear -bbx 32 'will be rOtated a number of 5 revolutions; dependent upoii the stp-up transmission ratio: This ratio can be the brder of 1 :250 virhereby urnsoutputis app'miamste- 5 iiiain the proper spacin for rs 3t ai" proyided' betwe input face 'ot thegea r boxflfiand thebracket ly'obtained T'om" clutch 3'45 spacer-ha the 206 In ordr "to 'dam pen -the rotational movements I of shait aran eddy current-'brake syst nt pm I vided comprising: 'ana'-lu1n'inum disli -3 si -mounted on the extremityof shaft'fl by a screw 40 which enters a threaded -bore in shaft" 3-Il D'isk ii fiis rotatable within air gaps 4I formed betweena i platei-42 of magnetic materialppole" pieces. 43 of an electromagnet haying windings 44 and the disk 1395- Y Pole pieces i'aremounted'on another IJlaite 45; also of maghetic m'aterial', by screws 45a-,=p1ate245 being .conventionallyrigidly heldby 1 casmgia I05 when' windings fl are excited, the" rotating brake" disk 39 'wil1' cause"anopposingtorque tobe exerted on it's*shaft 3 1 which in turn is 'exeitted onto shaft -I8!and"'rotor I6; whereby to I dampenthe rate "of. angular amovement-l thereof The amount 5 of dampening eflectwillvary as- =a== function of the magnetic-flux across'the airga'ps 2 4I; so that,.- by altering the effective width of" said ain gaps,- variation" can: bemade in the dampmg. a ti n; T0 effectirthis; plate '42 is I riveted to a" cylindrical capymemberi 46 which is intemally telescoped within. that end of theipart ofscasing I ll which houses the :brakee'de'lay unit I 4 member 46 being externally SCIEW-thlfiflidfiiflSat'i4-T4With' threads-complementary: toian internal screw 85 threadm48sformed in -'-the end ofithe casing; as? shownz. Adjustment of the "pdsitiomofqplatei42-: relative -.-to" the pole.- pieces' 43..' can: thusbe. made. byrotatingiend cap) .u'singiatool-therefor which. will engage: with. slots-5- 460i: m. the: cap, thereby i varying v the: damping effect; of.- thei eddy 'current: brake system; Graduated'iscale 49;"held: in; place.

by rivets; 4 9a assists:inz.easilyzobtainingathe1 desirediadjustmenh IniFig-k 1, the: adjustment; of.

the "cap :46. is:shown; at-1011c;- extreme= where: the: airgapf: 4 I ;-is at: a niinimum; By; withdrawing; the cap from thepositio'n shown .tomiden theiaiij gaps less iopposing torqueawillibez applied: by the: brake'zand'the timeirequired fon'mwementcfrom'; zero to.- the.-'- 90 position of rotor: I 6 c-willii-bes pro.=.-- 50 portionallyl' decreased; Bw. this: meansvadjuste mentu'ofs the; timeedeIayR-Tunction:of the timing; mechanismiofathemi'esentiinventidmcanlbemade: to vary the icontrol?operationiof rotor; I6 I from. one'or twoseconds tos-as muchzas several' 'minutes," depending onithe characteristics-of; the -.co operating. -elementse-thereofi Cooperatingzwith vthe motorsdrivetunit I3; and'; brake delay -unit I 4,. hereinbefo're i described, is".- the operating-unit :-I 5'. which...-acts -:.to .-.control--the;- operation" ofitheaunitsgl 3--'and I ,4. UnitrIS (Figs: Z 'and .3 )1 isarranged within the aloflwer portion of i' casingrifi and comprises:a;solenoid:assesm1y havirl'g twczhollow circul ancoils-iceand- 5-.I: arranged-5 concentrically: within the; housing and held; therein inconventionai manner; Withinvthe". inner coilthere isgproyided an ele'ment;.=52 held? thereinidconventionm manner; Element-.iztextends part-zeta the way into? the; 0011': 50- and hasiiatz the? endri'there'within a =frustro;-conica1 seat-.- 54: Seatr'5'4 sand; element252iare boredthroughout; to-.

permit? a; rod '55:t0 slide therethroughgo. bracket; 53 being also boreditofiallowa passageof saidrrodzr n -:55;- is. springsurged 5t'o prd'j ect I-into wean-.54.? H b in the position shownamfligazrby-zagueshapedfle' striker for r0d'55. At

plunger spri'ng 56 2 whiclr embraces the rodvin-xae 51*(Fief 5) "ther'earoun'd: and cambefiexed outfot: position by the rod when same;- is'i. moveds: to: theifright of JFigL-fi.

Slidingly embraced in a'i-sleevev 58.. mounted?- within .the. inner coil 5041s aplungerifl otmag neticmaterial which is 'a'dapteditcsb the ma'gneticfi'eld createdwhen; said 5| are excited." The forward-end of: has a conical nose 60 which 'complemen to the cone-shaped 'seat':.54'2 anditemiinatesi' an buttontl which: is screWed -into;the.%-'end:o th nose; this button being fiat: faced; tOlSBlVGl'flS."

its other end, .plun'gerz-I is bored, as at 62, to accommodate onez'endi o rod "63 which isJtied to the:plunger'-by; a'l'rivet-ir pin 64 traversing thesplungerrandi rod'in' alignedfi bores therein.

A spring '65 "exerts p parts 11, 19*and 8 0; other end in a recess within the housingv forming-a stop for e .mov'eth-bm cdilsif 5.0 and; the plungen:

ressurent one-end;through. on rod-- 63 and==seatsi-=at;;its: 66 formedsini'afiplugi-fi held: and: having shoulder: 68 movement of'rtheiplungeriug which stop limits the-'movement of theplungen under action of spring when this expaiidsz? Thus when the plunger'SBocciipisitsseatedZ sition of Fig. 3,- the-spring- 65 is compressed ahdi is acting against the magnetic force'causediby coils 50 and 5| whereas; when coils 50- and lII are deenergi'zed, the part'sassume the 'pc sition of Fig. 2 where the spring 65has relaxed or e panded to cause the plun'gertounseat itself froin seat 54 and assume it's extremelefthandposi tion.

Suitably mounted on bracket 53 is a closed" micro-switch 69 having; its actuator 10 in the path ofmoverneiit so that, in the positionof'Fig 2, -th closedand in the position otFi 3,-the switch-h been caused to open by'cont'a'ctof the-taper p? H of rod 55with the lever. switch fiil is the 01f f trol switch-for the application of' power motor drive unit-I3 and brake-delay "u'ni 1 as hereinafter-brought out, opening of; M ch 6 as in Fig. 3, will cause return of rotor"I6-t6 initial -starting-positio'n In the-position of'Fig. 3,-onl-y onecoil*5'0 is inr operation; this b'eing a holdin coil the elements 'inthe position-show f I gizing circuit to the holdingf coil"SIHs OntroIlBd by a' normallyclo sed relay} switcli fl2 lf when relay switch I2 ismom'entarilyfopnedi as f byf momentarily opening; its opera-tinigcircui position v action of spring 65. Switc rotor I 6 now turns an begun. Coil 5 I is mrmauy inoperative and is only lized as anactuating coil" tojcause' plunger be pulled" back; against 'the" action "oi f'spring 65; into the position of Fig. '3, where the holding-con? 50 can take over to retain'the paits-in the posfi tio'n' -shownl 'Ifheenergizing' 'circuit-to th aini-F' atin'gcoil-"54 is under-"the -co'ntrolbf *a nermany; open i switch 13; having n operating lever- 14 whicli can be' thrown into' 'switch -on"position hy an arm 'l5 mountedon shaf fl 8 to"move witl rth'e rotor' lfi; Thus, atthe end of trayel'pos'itidn ofl rotor I 6, switch 13 "will be closed and will cause} energizing of actuating 'coil -5 I fto move plunger" 5'9 tbthe position of Fi'g.- 3. Ii'i'thisptisitidfi; the spring 5 61i'will cause-ro'd 55' to mote toiallowfswitch 69:.tmop'en, thereby breaking thefmotdfunit-iicir cuit whichi is ztherrireturnedi toLthi-starting iposis;

, h 69 f h i 'eei j df dithe"timing delay' cyclefhasq when this is completed, the ready for further tion by spring 30. timing mechanism is again cyclic operation.

As hereinbefore set forth, one use to which the timing mechanism can be put is'in connection with hydraulic control means, for instance, for aircraft, where the application of hydraulic power need only be occasional, when called for by the pilot or other operator. As specifically illustrated, a valve assembly I2 can be readily controlled by the timing mechanism hereinbefore described. Valve assembly I2 comprises a main housing or cylinder 15 having ports A, B and C. A-spool-type valve I! operated therewithin, said valve having a recess I8 which accommodates one end of spring 85. Valve 11 is attached to rod 83 by a pin 80 which fits in a crosshole in rod 83 and cooperates with a washer 19, the valve being bored at 8| to receive the end of rod 63. Valve I1 slides in valve cylinder or housing 18in accordance with movements of plunger 59.

In Fig. 2, the holding coil I is deenergized and spring 65 controls the parts with the pressure port A in communication with the control port C, the flow of pressure being along the dotted linen-o. In Fig. 3, the holding coil is energized and the plunger 59 is seated, the pressure port A being in communication with. the return port B, the flow of pressure being along the dotted line :c-w, valve 11 having portions of its end cut away as at Ila to permit this flow.

It should be noted that if power failure occurs, the conditions will be assumed as in Fig. 2, so that the hydraulic control can be operated under such conditions.

This is an important factor when the device is used for aircraft operations particularly, since, if the electric wiring is destroyed or the power supply fails for any reason the parts of the operating unit will assume the position of Fig. 2, with the hydraulic pressure port A in communication with the control port C, whereby the hydraulic device to be controlled, such as the landing gear, can still function despite the crippling of electrical supply. Whether the pilot is aware of the disablement of the electric supply or not, the hydraulic unit can still function because coil 50 will have been deenergized and spring 85 will have placed the operating unit on the pressure to control side through port A to port C.

In'order to more clearly explain the operation of the timing mechanism when used for hydraulic control, as specifically illustrated, reference is made to the wiring schematics, Figs. 6 and '7.

Referring to Fig. 6, where like numbers have been given'to the parts illustrated in Figs. 1-5 of the drawings, a storage battery 82 or like supply of electric power is shown, having its positive terminal connected by lead 83 to one side of the coil 84 of relay 12 through a plurality of control switches 85 and 88, these being normally closed switches, arranged in series connection with coil 84. The other side of coil 84 is connected by lead 81 to the grounded return lead 88. In this position, coil 84 attracts the relay switch arm 89 of relay 12 holding it, against the spring return 50, against contact 9| which connects with one terminal 92 of holding coil 50 through lead 93. The other terminal 94 of coil 50 is connected to the ground return 88 through lead 95. Thus, with relay I2 in operative condition and switches 85 and 85 closed, holding coil 50 will be in position to hold plunger 59 on its seat, as in Fig. 3, with switches 50 and 13 in open position. The hydraulic flow will thus be in by-pass condition from pressure port A to return port B. If now either or both of switches and 86 are opened, for example, by the pilot or other operator, the relay coil 84 will be deenergized, contact between arm 89 and contact 9| will be broken by spring 90 and holding coil 50 will be deenergized and plunger. 58 will move, under urge of spring 55, to the position shown in Fig. 2. This will cause switch 89 to be closed by action of rod 55. Since the switch arm I0 of switch 69 is connected to negative lead 88 and the contact for switch 89 is connected to one side of the common lead 96 for the motor field winding 29 and brake winding 44, this will complete the return connection to the motor and brake units.

The positive common lead 91 for windings 44 and field windings 29 is connected by lead 91a to contact 9I. By connecting coils 29 and 44 in parallel, with common leads 96 and 91, fluctuations of input voltage will have no serious effect on the time cycle produced since both motor and brake will be equally affected.

Switches 85 and 86 are of the momentarilyoff type, namely, they are lagged or dampened so that they are only opened for a period of time necessary to initiate the function of deenergizing relay I2 and thereafter return automatically to closed position as in Fig. 6. Therefore, when switch 89 completes the negative or return circuit for the motor-brake unit, the positive side thereof is connected to the positive lead 83 through the now closed switch 89-9I. The motor-brake assembly now commences to rotate as previously described.

After the time cycle has been completed, the arm 15 on shaft I8 will be in position to close switch I3, the contact 89 of which is connected by lead I00 to one terminal IOI of actuating coil 5|, the other terminal I02 being connected by lead I03 to lead and ground return 88. By this means, the actuating coil in is energized adding its magnetic influence to the holding coil 50, which is now energized by the closing of arm 89 of relay I2 but which alone is not powerful enough to overcome the spring 65 and the inertia in the system and can only serve to hold the plunger against its seat when it has been seated. The plunger now moves to the right, from the position of Fig. 2 to the position of Fig. 3, the rod 55 opens switch 89, thereby breaking the return lead 98 and deenergizing the windings 44 and 29. The motor-brake unit will now be at rest, ready for further actuation, the parts bein in the condition schematically shown in Fig. 6.

r In Fig. '7, a modified form of circuit is shown in which series switches 85 and 85 are replaced by parallel switches I04, I05 and I06 which are connected on one side by a lead I01 to the positive side of battery 82 and on the other side to the coil 84 of relay I2, the other terminal of coil 84 going to the negative grounded side of the battery by lead 81. Switches I04-6 are normally open lag-type switches and are momentarily closed to activate coil 84 to draw arm I08 away from contact I09 against the action of spring H0, thereby causing the holding coil 50 to be deenergized as previously described. The holding circuit for coil 50 in the modified form of Fig. '7 is by contact of arm I08 under pressure of spring IIO with contact I09 when the relay coil 84 is deenergized. Thus, the form shown in Fig. 7 obviates the necessity of having coil 84 energized during the long periods of non-use of the control, only holding coil 50 being ener gized during such inactive periods.

The operation of the device can be best described in connection with its application to control of hydraulic apparatus for operating the landing gear of an airplane, as exemplified hereinbefore. Assuming the aircraft to be airborne the timing unit II at rest with motor unit I3 at rest and deenergized.

When the pilot decides to lower the landin wheels upon approach to a landing, it is necessary to change the conditions from those of Fig. 3 to those of Fig. 2 to first apply pressure from port A to control port C and thence to the hydraulic system controlling operating of the landing wheel raising and lowering mechanism.

In the control circuit of Fig. 6, switches 85 and 86 are normally closed and relay coil 84 is normally energized to hold arm 89 upon the contact 9|, against spring pressure of spring 90. If the crewman responsible for the landing gear operation now opens either switch 85 or 86, r lay 12 will have its coil 84 deenergized and arm 89 will be spring urged out of contact with contact 9|. This will break the circuit to holding coil 50 (through lead 93) causing spring 65 to draw plunger 59 to the left into the position of Fig. 2. Thus, pressure port A now communicates with control port and the landing gear system is in condition for operation in conventional manner.

Since switches 85 and 06 are of the momentarily-oif type, they will return to the position in Fig. 6 after a time sufficient to initiate the action just described. Now, relay 12 is again energized as is holding coil 50 but the parts remain in the position of Fig. 2 because coil 50 is incapable, of

itself, of overcoming the power of spring 65. Due

to-the closing of switch 69 by movement of rod 55 to the left in Fig. 2, the motor and brake windings 29 and 44 will remain excited through lead 98 until the time-cycle determined by the brake delay unit I4 is completed and switch 13 is closed onto contact 99 through arm 15. Closing of switch 13 causes actuating coil 5I to be energized through lead I00 whereby the plunger 59 is moved to the right, to the position ofFig. 3. In this position, switch 69 is: again open, disconnecting the motor windings 29 and brake windings 44, thus stopping the motor. Spring 30 (Figs. 4 and 5) now returns rotor I6 to zero, or starting position, thus removing switch 13 from contact 99, so that actuating coil 5| is disconnected from the battery circuit (lead 83). The parts are now all in the position of Fig. 3, ready for further operation when called for.

While the parts are in the position of Fig. 3, should power failure occur for any reason, the parts will immediately move to the position of Fig. 2, since relay 12 and holding coil 50 will be deenergized and thus spring 65 will come into action. This places the hydraulic system in operative position from pressure port A to control port C, so that the landing gear can be operated. Thus, the timing mechanism of the present invention has a further safety factor since under power failure conditions the unit will assume a position of positive control and will not prevent operation of the function being controlled, such as the landing gear operations.

When using the circuit of Fig. 7 any of the normally open switches I04, I05 or I09 can be manuallyclosed when it is desired to lower the landing brief lag of a predetermined or the wheels, this causing energizing of relay 12 to move arm I08 from contact Since the switches I04, I05 and I06 are of the normally-open type which after being momentarily closed open again after a predetermined time lag, the switches will again open to deenergize relay 12 and energize holding coil 50 through closing of arm I08 onto contact I09 as in Fig. 7, the rest of the operation then being as given above.

While hereinbefore reference has been made to a drive unit I3 having a rotor l6 and stator 22 and 29, it is possible to use any equivalent electrodriving purposes. For exmember actuated by an electro-magnet driver, such as a solenoid coil and plunger and damping means equivalent to the brake unit I4 can be provided therefor, within the spirit and scope of the present invention.

Obviously, a plurality of timer-mechanisms according to the present invention can be employed for multiple action of functions. For example, where positive wheels-up-wheels-down procedure forlanding gear is required, one timermechanism can be used for the wheels-up function and a separate timer-mechanism can be used for the wheels-down function. In a like manner, where several gun turrets are to be moved into Any other function which is hydraulically controlled may be governed by the timer-mechanism herembefore set forth and described, whereby to remove the hydraulic pressure from the apparatus to be hydraulically controlled until same is actually needed and to only apply such pressure while it is needed.

While the timing mechanism has been specifically described with respect to hydraulic controls which are only utilized when specifically needed, it is obvious that various modifications and uses timing mechanism can be had within the spirit and scope of the invention as described, and the claims appended hereunto. For example,

-spring may be operated so that the positions in Figs. 2 and 3 are reversed operations, whereby in Fig. 2 the holding coil would be operative against the-spring, to cause one control condition; and in Fig. "3 the holding coil would be deenergized and the plunger spring-urged to the alternative control condition.

Furthermore, while the timing mechanism has been shown and described as a composite assembly with its several cooperating parts of motor drive unit I3, brake-motor unit I4, operating unit I5 and valve assembly I2 all within one casing l0, it is obvious that one or more of these units may be remotely arranged without changing the operation or cooperation of parts. 1. When using the time mechanism as a composite assembly within one casing, the various electrical connections to the coils, switches and other parts can be conveniently brought from externally of the assembly for internal wiring by a conventional form of electrical multi-pin connector III suitably mounted in an end plate II2 fitted over one end of easing I0.

The advantages in use of time-delay mechanism of the type generally set forth are many, particularly in aircraft and similar uses. The

,tially fool-proof.

' brake moves to preselect the an active control position;

tion of its rotor of about 90 l l assembly is light-weight, compact and substan- It lends itself 1 to. operation in position relative to any attitude of It can operate on a small amount of power, such as the 22 to volts or D. C. current usually available on aircraft. The 'motor unit may be or the non-commutator'type, eliminating dangers from sparking. It will operate under great variations of ambient conditions. By using a control unit according to this invention any physical the aircraft.

.the hydraulic pressure, which may be as high as 3000 p. s. i., can be removed from control apparatus such as that used to raise and lower landing gear or expose and withdraw gun turrets from the aircraft, until such time as the function or operation is demanded, when by simply closing a switch, the control meansis put in service in the hydraulic system for use for one or-more' control functions.

We claim:

1. A timing mechanism comprising in ,com-

,bination, a control actuating means having two positions of control; a spring cooperating with said actuating means and biasing it to one of said positions of control; electro-magnetic means, including a solenoid holding coil, for, positively holding said actuating means in one control ,position against a spring bias when energized; means for deenergizing said electro-magnetic means to permit said actuating means to occupy the other control position under. said spring bias; an electric motorv having arotor and a stator; means to limit the angular movement of said rotor in one direction only to 90; damping means including an eddy current brake, cooperating with said motor to-delay thetime-cycleduringwhich said rotor moves through its limited angular displacement; means toadjust the damping means by varying the airgap in which the eddy current delay; cyclepof said motor; means associated with said rotor to maintain said actuating means; insaid other control position during'saidmotor time-delay cycle; and automatic means to return said actuating, means .to said one control position after the time-delay cycle has ended, including. an actuating solenoid coil acting to move said actuating meanaan'd a switch located in the circuit of said activating solenoid coil and closed of angular movement.

I2. A timing mechanism comprising in combination a control member having a dormant and electro-magnetic means, including a-solenoid holding coil, to hold said control member normally in said dormant position; an electric motor having angular'rotain one direction only; delay means including an eddy-current brake rotating in an air gap and driven by said motor to delay the time-cycle of angular movement; means to adjust the air gap of said brake to vary said time-cycle; switching means for deenergizing said electro-magnetic holding coilmomentarily and thereafter re-energize same; means for-moving said control member to-activeposition when said electro-magnetic means is deenergized comprising a spring, said spring being stronger than the holding coil, thereby preventingsaid control member from moving from said active position during the time-delay cycle of rotary movement; means for deenergizing said motor at the ,end ofsaid cycle to stop same; a torsion spring {or returning said ,rotorto starting position when deenergized;

bysaid-rotor at its limit a solenoid actuthan said first-mentioned spring;

of less than. 360

v.tio-n against action response. membertobe held thereby said electrov:bination, .acontrol member adapted to 'be vin either, an active or a dormant position;-elecelectroemagnetic responsive ,coil energizedto maintain said control member when in said deenergize said motor, and

ating coil cooperating with-said control member and when energized exerting 'a'force stronger and a switch closed momentarily by said rotor at the end-of its rotation, and located in the circuitof said actuating coil. I

-3."A' timing mechanism comprising in combination an electro-magnetic response :member having a dormant and an active control position; electro-magnetic means including a solenoid holding coil to hold said response member normally in said dormant position; an electric motor having unidirectional driving angular rotation and spring loaded rotation'in theopposite direction; a brake-delay driven by said motor and applying an opposing torque to delay the time cycle of angular movement; means to vary theopposing torque of said brake to vary, said time-cycle means; switchingmeans operated'rby said response member fordeenergizing said electroemagneticw holdingw coil momentarily; ,a coiledspringacting on said response member tomove. same to active position when said ,electro-magnetic. means is ,deenergized, said coiled springlbeing. strong. enough to prevent said response .memberfrom moving from said active positionunder urge of the reenergizedholding :coilduring the time-delay cycle of. rotary movementpswitchmeans for deenergizing saidmotor ..a-t,the end of said. cycleoperated bymovement of said response member to dormantposition; and. an actuating. coil for said. solenoid momentarily, energized in one position ofsaid-motor for moving said controlmember into dormant posiof said springl-to -causei-said magnetic holding coil.

4. :A timing mechanism comprising commoved tro-magnetic means includingra solenoid and an plunger for moving said control member; ,aholding zcoil for said solenoid; a. relay for maintaining said holding control. member in one of its positions; master switching means for governing the energizing of said holding ,coil

. and .saidrelay; mechanical means for moving said control member-to' the other position when said holding coil is deenergized; an=.electricmotor ,having a, rotor and stator,saidzrotor'having;lim-

-ited rotation and in -,one I direction of rotation only when excited; means movedrbymotation of said: rotor, for storing up sufilcient force to return the rotor to itsstarting; point in the other; direcition; of rotation: when the; motor, is-,deenergized;

a brake driven by said :rotor; .an actuating 'ccoil ,for said solenoid acting withsaid-holding coil to move said plunger and -controlmember *torsaid one .position against saidzmechanical means; a

switchoperatedxby said rotor tocauseexcitation of saidactuatingcoii; aiswitcir actuated by said one position :to switch means "for energizing said holding coil and relay while said motor isenergized and prior to the excitation of said actuating coil.

'5. A timing -mechanism comprising in combination a control member adapted to be moved in either an active or a dormant position; electro-magnetic means including asolenoidand an electro-magnetic responsive plunger for'moving said control member; aholding coil for said solenoid; a normally-on relay-for maintaining said rotor aria s W non or mass th'a;i'1-'36U*,andinoving in one direcating coil for said electro-magnetic responsive "said control member; a holding coil for said solenoid; anormally-ofi relay for maintaining radi g coil energized artisan-control inc" in one or its no trons; hncnnanyon tchin'g ,s'a'iii holding "coil is aeenergizea g said switching meana'an e ectric motor-having it an rotornavmg limited rotation o rotation only elicited; eddy rent brake moving in an gap and ant s by said motor through aster-op speed transmission .,gear; .means to vary the area of the air gap to vary the time-delay cycle of the motor; aetnsolenoid acting .with said holding coil to move said plunger and control mefnberto said one position; ainormally-open switch operated in one position of themotor tobe closed to energize said actuating coil momentarily; and a normally clcsedswitch opened by said control member when :held in said one position, said switch deenergizing said motor.-

-,6, A timing mechanism comprising in combination a control member adapted to be moved in either an active or a "dorm-ant position; electro-magnetic means including a solenoid and an plunger for moving said holding coil energized and said control member in one of its positions; normally-01f switching means for governing the energizing of said holding coil and said relay; spring means for moving said control member to the other position when said holding coil is deenergized by closing said switches to energize said relay; an electric motor having a stator and rotor, said rotor having limited rotation of less than 360 and in one direction of rotation only when excited; an eddy current brake moving in an air gap and driven by said rotor through a step-up speed transmission gear; means to vary the area of the air gap, to vary the time-delay cycle of the rotor; an actuating coil for said solenoid acting with said holding coil to move said plunger and control member to said one position; a normally-open switch operated in one position of the rotor to be closed to energize said actuating coil momentarily; and

a normally-closed switch opened by said control member when held in said one position, said switch causing deenergizing said rotor.

7. A timing mechanism comprising in combination a control member adapted to be moved in either an active or a dormant position; electro-magnetic means including a solenoid and plunger for moving said control member; a holding coil for said solenoid; a normally-on relay for maintaining said holding coil energized and said control member in one of its positions; switching means for governing the energizing of said holding coil and said relay; spring means for moving said control member to the other position tion of rotation when deenergized; an eddy current brake moving in an air gap and driven by said rotor through a step-up speed transmission gear; means to adjust the area of the air gap to vary the time-delay cycle of the rotor; an actusting coil roimarathon her to said one p sifticnga switch-op means having anaetive aha a delay device and operable; at the end corn and ing coil to move said 1511i on'ep'os'ition or the oto'r to be closed and said -act anng j mom tan closed switch .afctu'a d by sa d coiitr v i I when in sai'd one posit on to can; deencrg'iz g or said'rotor and switch means for one s said holding coil anareiay; running and prior "totl're 'eiifcita on ating'c'oi.

s. In emanation,

and means 'f bi'a'sin'gs'faid actuatm its active position; a first oird uit mama rent source, a swoon and an elect with a movable care smartly connec actuating means to over-come said -b'iasmgmea and to move said actuating means to its dor position when said switchiis' closed ands'aiid e I tro-magiiet is energized; a secofidcircilit "ifilufling an electrical time adage vice automat l y operable upon; movement ofsaid actuating means its active position to permitsu ch position-to .be .niai-ntained "for a predetermined time interval, and switch means associated with such time il predetermined interval toclose said first circuit, to reehergize said: electr c-magnet and tomove said actuating means to its dormant position; whereby said actuating means will be maintained in active position for a predetermined time interval in the event the electric circuit should not fail, and will be retained indefinitely in active position in the event the electric circuit should fail.

9. In combination with a control actuating means having an active and a dormant position and spring means for biasing said actuating means to its active position; a first circuit including a current source, a switch, and an electro-magnet with a movable core operably con nected to said actuating means for overcoming said spring biasing means and for moving said actuating means to its dormant position when said switch is closed and said electro-magnet is energized; a second circuit including a switch event of circuit failure said control actuating means is moved to and sition.

dormant position when said a movable valve member .said return port-into communication; spring means normally biasing said valve element to its active position; a first circuit including a switch, a current source and an electro-magnet having a movable core operably connected to said valve element to overcome the bias of said spring and to movesaid valve element to and hold it in said switch is closed and said electro-magnet is energized; a second circuit including an electrical time delay device automatically operable upon movement of said valve element to its active position to permit such position to be maintained and for fluid to flow from said source to said control port for a predetermined time interval, a switch means associated with such time delay device and operable at the end of such predetermined interval to close said first circuit, to reenergize said electro-magnet and to move said valve element to its dormant position, whereby said pressure port is connected to said return port until the switch of the first circuit is again opened or there is anelectrical failure of said circuit. 7

11. In combination with a valve having a casing provided with pressure, return and control ports, cooperating with said casing for connecting the pressure port to either the return port or the control port, and means for biasing said valve member to the position in which said pressure and control ports are con- ,nected; an electro-niagnet having holding and actuating coils and a movable core connected to said valve member; a switch opened by said core when the core has been magnetically actuated; a normally-open switch located in the circuit of said actuating coil; electrical means for temporarily closing said last mentioned switch after a time interval following the closing of the switch operated by said core; a normally-closed switch through which current is supplied to said holding coil, and to said actuating coil when said normally-open switch is closed; and means for temporarily opening said normally-closed switch; whereby said valve member is moved to and held in the position in which said pressure and return ports are connected, and upon the temporary opening of said last-mentioned switch said valve member is permitted to move for a limited time to the position in which said pressure and control ports are connected.

STANLEY J. SMITH. I JACK ISREELI.

References Cited in the file Of this patent UNITED STATES PATENTS 

